Converting % to Hydraulic Pressure to Plastic Pressure

Hello All,

Thanks to a good discussion by Joel, JayDub, Brent and Rick on another thread, I thought I would post this here.

Many a times I come across % settings on the machines and processors need actuals. There is a very simple procedure to find out the actuals. Of course, as Joel points out you will need a hydraulic gage to display some pressure somewhere!

Here is what you do (WITH SAFETY IN MIND PLEASE!!!!)

1. Make sure the barrel is up to the molding temp.
2. Pull the barrel back from the mold as if you were purging it.
3. Set your speeds to slow and purge out all the plastic so that the screw is bottomed out.
4. You are probably in the hold/packing pressure area of the barrel and so set those pressure to 50%
5. Watch the actual the pump is giving you and note that down.
6. Then set it to 75% and note the actual.
7. Then set it to 100% and note the actual.

By simple math, you will figure out 'If 100% is 2000 psi, then 1% is 20 psi'. Therefore if I am applying 30 %, the pressure applied is 30 times 20 = 600 psi.'. The reason you do a 50% and a 75% is to see if you get a linear relationship. Just as above, calculate the 50% and the 75% and see if they match the actuals.

Then assuming you know the IR of the machine, Plastic Pressure = Hyd Pressure X IR.

Hope this helps.

Regards,
Suhas